Despite the cariogenic role of suggested from recent studies, oral acquisition in children at high risk for early childhood caries (ECC) and its association with cariogenic bacteria remain unclear. Although ECC disproportionately afflicts socioeconomically disadvantaged and racial-minority children, microbiological studies focusing on the underserved group are scarce. Our prospective cohort study examined the oral colonization of and among 101 infants exclusively from a low-income and racial-minority background in the first year of life. The Cox hazard proportional model was fitted to assess factors associated with the time to event of the emergence of oral and . Oral colonization started as early as 1 wk among 13% of infants, increased to 40% by 2 mo, escalated to 48% by 6 mo, and remained the same level until 12 mo. in saliva was detected among 20% infants by 12 mo. The emergence of by year 1 was 3.5 times higher (hazard ratio [HR], 3.5; confidence interval [CI], 1.1-11.3) in infants who had early colonization of oral compared to those who were free of oral ( = 0.04) and 3 times higher (HR, 3.0; CI, 1.3-6.9) among infants whose mother had more than 3 decayed teeth ( = 0.01), even after adjusting demographics, feeding, mother's education, and employment status. Infants' salivary abundance was positively correlated with infants' ( < 0.01) and levels ( < 0.05). Infants' oral colonization of was positively associated with mother's oral carriage and education ( < 0.01) but negatively associated with mother's employment status ( = 0.01). Future studies are warranted to examine whether oral modulates the oral bacterial community as a whole to become cariogenic during the onset and progression of ECC, which could lead to developing novel ECC predictive and preventive strategies from a fungal perspective.